Diffusion transfer article and process using humectant in emulsion layer

ABSTRACT

PHOTOGRAPHIC PRODUCTS FOR USE IN DIFFUSION TRANSFER PROCESSES INCLUDING A LIGHT-SENSITIVE SILVER HALIDE EMULSION LAYER AND WHEREIN THE EMULSION LAYER FURTHER INCLUDES A PHOTOGRAPHICALLY INNOCUOUS HUMCCTANT IN AN AMOUNT SUFFICIENT TO LOWER MATERIALLY THE PROCESSING TIME FOR FORMING THE TRANSFER IMAGE.

United States Patent Oflice 3,666,460 Patented May 30, 1972 3,666,460DIFFUSION TRANSFER ARTICLE AND PROCESS USING HUMECTANT IN EMULSION LAYERLeonard C. Farney, Melrose, Mass., assignor to Polaroid Corporation,Cambridge, Mass. No Drawing. Filed Jan. 11, 1966, Ser. No. 526,673 Int.Cl. G03c 5/54 US. Cl. 96-29 14 Claims ABSTRACT OF THE DISCLOSUREPhotographic products for use in diffusion transfer proceses including alight-sensitive silver halide emulsion layer and wherein the emulsionlayer further includes a photographically innocuous humectant in anamount sufficient to lower materially the processing time for formingthe transfer image.

This invention relates to photography and, more particularly, to novelproducts and processes for preparing visible images by diffusiontransfer.

A primary object of this invention is to provide novel photographicemulsions and film units containing the same.

Another object is to provide a novel diffusion transfer process forpreparing silver images wherein the processing time and/or the amount ofprocessing composition necessary to provide a silver transfer image of agiven desired density is materially lowered.

Still another object is to provide novel photographic products andprocesses for preparing a transfer image in a layer above thephotographic emulsion, which image need not be separated from theemulsion subsequent to processing in order to be viewed.

Other objects of the invention will in part be obvious and will in partappear hereinafter.

The invention accordingly comprises the process involving the severalsteps and the relation and order of one or more of such steps withrespect to each of the others, and the product possessing the features,properties and the relation of elements which are exemplified in thefol: lowing detailed disclosure, and the scope of the application ofwhich will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention,reference should be had to the following detailed description.

It has herefore been known to incorporate plasticizers in photographicemulsion layers to prevent curling and/ or the tendency of the emulsionlayer to crack when it is flexed, especially at low humidities.

It has now been found, quite surprisingly, that the presence in thephotographic emulsion layer of an effective amount of a photographicallyinnocuous humectant materially lowers the processing time and/or theamount of processing composition necessary to form a silver image bydiffusion transfer. This is apparently, at least in part, due to theability of the humectant to retain water in the emulsion matrix, e.g.,in the gelatino matrix of a gelatino silver halide emulsion, which inturn minimizes shrinkage, or stated another way, minimizes the swellingnecessary for processing, thus lowering the induction time and/or thetime required for the soluble silver complex to transfer to the layer orstratum where the silver transfer image is formed. In addition, undergiven processing conditions it is possible to obtain a silver transferimage having a desired density with less sliver in the photosensitiveemulsion.

As used herein and in the appended claims, the term photographicallyinnocuous humectant denotes a humectant which is not harmful or whichdoes not hinder the photographic process, i.e., does not adverselyaffect the light-sensitive emulsion or the processing of a developableimage produced 'by photoexposure thereof.

As examples of suitable photographically innocuous humectantscontemplated by the present invention, mention may be made ofwater-soluble polyhydroxy com pounds such as a-methyl glucoside,glycerine, etc. The amount of humectant needed will vary according tothe structure and character of the film unit and the developingcomposition employed as Well as the processing conditions. Generally, atleast 25% of humectant based upon the weight of gelatin in the emulsionand preferably at least 40% should be employed for optimum results.Particularly good results have been obtained when the percentage ofhumectant is or more. In any event, the selection of the particularamount of humectant to be employed will be readily apparent to thoseskilled in the art in view of the present disclosure. Accordingly, asused herein and in the appended claims the term effective amount denotesthe amount of humectant necessary to obtain the desired results, e.g.,the amount of humectant necessary to obtain the desired lowering ofprocessing time and/or amount of processing composition necessary.

The present invention is particularly useful in photographic systemssuch as are described and claimed in the copending application of EdwinH. Land, Ser. No. 519,- 995 filed concurrently as a continuation-in-partof application Ser. No. 368,622 filed May '19, 1964, both of which arenow abandoned, and the copending application of Edwin H. Land andLeonard C. Farney, Ser. No. 519,- 884 filed concurrently as acontinuation-in-part of application Ser. No. 368,621 filed May 19, 1964,both of which are now abandoned.

As is disclosed in these applications, a photographic film assemblyincluding a layer containing a light opacityproviding material may beexposed to a light source on the same side of the support for the filmassembly as the layer of opacity-providing material and then processedto form a negative image and a positive transfer image in a stratumsituated above the layer of opacity-providing material. Thisopacity-providing material is present in an amount sufficient to maskeffectively the negative image but not sufficient to precludephotoexposure of the light-sensitive material in the-film assembly, sothat there is formed a composite print which contains both a negativeand a positive image but which is viewable by reflection as a positivereproduction of the original subject matter. The opacity-providingmaterial, which is preferably white or substantially colorless, furtherserves to provide the background for the positive image.

In application Ser. No. 519,995 the layer of opacity providing materialis situated over a layer containing a light-sensitive silver halideemulsion; while in application Ser. No. 519,884 the opacity-providingmaterial is situated in same layer as the light-sensitive silver halideemulsion and a second or additional layer of opacity-providing materialmay also be provided over the layer containing the silver halideemulsion.

Any of the aforementioned film asemblies may contain an outer layercomprising a silver receptive Stratum, i.e., a stratum containing atleast one silver precipitating agent, or the silver precipitating agentmay be present initially in the processing composition. 7

The following examples show by way of illustration and not by way oflimitation the use of this invention in photo graphic systems such asdescribed and claimed in the aforementioned two copending patentapplications.

EXAMPLE I A first film unit was prepared by coating on a paper basesupport a light-sensitive silver halide emulsion layer containing 0.071gm. of silver and 0.61 gm. of gelatin per sq.

ft. of surface area. Over this light-sensitive layer was then applied alayer of opacifying material containing 0.45 gm. of titanium dioxide and0.045 gm. of gelatin per sq. ft. On top of this was coated a silverreceptive stratum containing 0.001 gm. per. sq. ft. of lead sulfide and0.11 gm. per sq. ft. of gelatin. A second film unit was prepared whichwas substantially identical to the cfirst film unit except that thelight-sensitive layer also contained 0.25 gm. of tit-methyl glucosideper sq. ft. of surface area.

The above film units were exposed and developed in exactly the samemanner, namely by exposing each film unit to the same subject matter forone second and then running the thus-exposed film unit through a bathcontaining the following processing composition:

Water8400.0 cc.

Sodium hydroxide96.0 gm.

Sodium sulfite-255.0 gm.

Potassium thiosulfate-147.0 gm. 4-amino-2,6-dimethylphenol90.0 gm.Phenylmercaptotetrazole-0.09 gm.

The exposed film units were immersed in the bath for about one secondfollowed by an additional twenty seconds dark time. The silver imageobtained from the first film unit (the one with no humectant) had a D of0.40 while the silver image obtained from the second film unit had a Dof 1.25, thus demonstrating the materially greater D obtained at shortbath times by having a humectant present in the light-sensitive layer.

EXAMPLE II Example I was repeated, except that the exposed film unitswere immersed in the processing bath approximately three times as long.The first film unit provided an image having a D of 1.40 (in contrast tothe 0.40 obtained in Example I) while the second film unit containingthe humectant provided a image having a D,,,,,,, of 1.08.

From Example II it will be observed that the film unit with no humectantwas immersed in the processing bath approximately three times as long asthe film unit with the humectant of Example I in order to obtain apositive image having a comparable D thus demonstrating how the presenceof the humectant materially lowers the processing time required toobtain a positive image of a given D This shorter processing time is ofparticular significance in document duplication systems employing thepresent invention.

The following additional examples are further illustra tive of the filmunits contemplated by this invention.

EXAMPLE HI On a paper base support was coated a light-sensitive emulsionlayer containing per sq. ft. of surface area 0.0059 gm. of silver, 0.22gm. of gelatin, 1.72 gm. of titanium dioxide, 0.24 gm. of Cab-O-lSil(trademark of Godfrey L. Cabot, Inc. for a fire-dry 99% pure fumedsilica with a particle size of 0.015 micron, surface area of 200 mP/gm.bulk density of 2.3 lb./cu. ft.) and 0.053 gm. tit-methyl glucoside. Ontop of this was coated a silver-receptive stratum containing 0.001 gm.per sq. ft. of lead sulfide and 0.22 gm. per sq. ft. of gelatin. Theexposure and development in the manner described in Example I provided apositive silver reproduction of excellent density and contrast.

EXAMPLE IV Example III was repeated, substituting for the lightsensitiveemulsion layer, a layer containing per sq. ft. of surface area 0.0065gm. of silver, 0.25 gm. of gelatin, 1.44 gm. of titanium dioxide, 0.20gm. of Cab-06H and 0.l2 gm. of tx-mfifl'lyl glucoside. A comparablepositive silver reproduction was obtained.

4 EXAMPLE v On a paper base support was coated a light-sensitive silverhalide emulsion layer containing per sq. ft. of surface area 0.05 gm. ofsilver, 0.39 gm. of gelatin, 2.00 gm. of titanium dioxide and 0.34 gm.of a-methyl glucoside. Over this light-sensitive layer was then applieda layer of opacifying material containing per sq. ft. of surface area1.01 gm. of titanium dioxide and 0.055 gm. of gelatin. On top of thiswas coated a silver-receptive stratum similar to that described inExample 1. Exposure and development in the manner described in Example Iprovided an excellent positive silver reproduction.

EXAMPLE VI On a paper base support was coated a light-sensitive silverhalide emulsion layer containing per sq. ft. of surface area 0.050 gm.of silver, 2.00 gm. of titanium dioxide, 0.213 gm. of gelatin and 0.34gm. of tl-mfithyl glucoside. Over this light-sensitive layer was thenapplied a layer of opacifying material containing per sq. ft. of surfacearea 0.86 gm. of titanium dioxide and 0.043 gm. of gelatin. On top ofthis was coated a silver-receptive stratum as in Example V. Exposure anddevelopment in the foregoing manner provided a positive silverreproduction comparable to that obtained in Example V.

While the present invention may be employed in diffusion transferprocesses for preparing silver images generally, from the foregoingillustrative examples it will be appreciated that the present inventionis particularly useful in photographic products and processes forpreparing composite prints viewable by reflected light as a positivereproduction, such as are described and claimed in the aforementionedcopending applications, Ser. No. 519,995 and Ser. No. 519,884 filedconcurrently. In this respect, the present invention may be employed inthe preparation of composite prints in conjunction with the electrolyticdevelopment techniques described and claimed in the copendingapplication of Edwin H. Land, Ser. No. 519,885 now US. Pat. No.3,362,823 and Ronald F. Cieciuch, Ser. No. 519,886 and now US. Pat. No.3,549,363, both filed currently.

Since certain changes may be made in the aboce process and productwithout departing from the scope of the invention herein involved, it isintended that all matter contained in the above description shall beinterpreted as illustrative and not in a limiting sense.

What is claimed is:

1. In a photographic product for forming a composite pr nt which apositive image is formed over a negative image, said composite printbeing viewable as a positive reflection print without separation of saidtwo images, said product comprising a support substantially opaque tovisible light and having thereon a first layer containing alight-sensitive silver halide emulsion and a second layer situated abovesaid first layer and containing a light opacity-providing material in anamount sufficient for masking elfectively a negative image formed byexposing said photographic product and deyeloping said exposed productto form said negative image in said first layer and a positive image ina stratum on said second layer, the amount of said material beinginsufficient to preclude photo-exposure of said silver halide from alight source on the same side of said support as said two layers, saidmaterial further providing a background for viewing said composite printby refiected light as a positive image; the improvement which comprisesincluding in said first layer a photographically innocuous humectant inan amount sufiicient to lower materially the processing time for formingsaid transfer image.

2. A photographic product as defined in claim 1 wherein said humectantcomprises a-methyl-glucoside.

3. A photographic product as defined in claim 1 whercin said emulsioncomprises a gelatino silver halide emulsion and at least 25% ofhumectant based upon the weight of gelatin in said emulsion is presentin said layer.

4. In a photographic product for forming a composite print in which apositive image is formed in a stratum over a negative image, saidcomposite print being viewable without separation of said two images asa positive reflection print, said product comprising a support havingthereon a layer containing a light-sensitive silver halide emulsion,said layer further including a light opacityproviding material in anamount sufficient for masking effectively a silver image formed in saidlayer by exposing said photographic product and developing said exposedproduct to form said negative image in said layer and a positivetransfer image in a stratum above said layer containing said negativeimage, the amount of said material being insufficient to precludephotoexposure of said silver halide from a visible light source on thesame side of said support as said layer, said material further providinga background for viewing said composite print by refiected light as apositive image; the improvement which comprises including in said layera photographically innocuous humectant in an amount sufficient to lowermaterially the processing time for forming said transfer image.

5. A photographic product as defined in claim 4 wherein said humectantcomprises a-methyl-glucoside.

6. A photographic product as defined in claim 4 wherein said emulsioncomprises a gelatino silver halide emulsion and at least 25% ofhumectant based upon the weight of gelatin in said emulsion is presentin said layer.

7. In a photographic product for forming a composite print in a stratumover a negative image, said composite print being viewable as a positivereflection print without separation of said two images, said productcomprising a support having thereon a first layer containing alightsensitive silver halide emulsion and a light opacity-providingmaterial, and a second layer situated above said first layer andcontaining a light opacity-providing material, said material in said twolayers being present in an amount sufiicient for masking efiectively asilver image formed in said first layer by exposing said photographicproduct and developing said exposed product to form said negative imagein said first iayer and a positive transfer image in a stratum abovesaid second layer, the amount of said material being insufficient topreclude photoexposure of said silver halide from a visible light sourceon the same side of said support as said two layers, said materialfurther providing a background for viewing said composite print byreflected light as a positive image; the improvement which comprisesincluding in said first layer a photographically innocuous humectant inan amount suflicient to lower materially the processing time for formingsaid transfer image.

8. A photographic product as defined in claim 7 wherein said humectantcomprises u-methyl-glucoside.

9. A photographic product as defined in claim 7 wherein said emulsioncomprises a gelatino silver halide emulsion and at least 25 of humectantbased upon the weight of gelatin in said emulsion is present in saidlayer.

10. A photographic process wherein a layer containing a light-sensitivesilver halide emulsion is exposed through a layer of lightopacity-providing material positioned thereover to form a developableimage and said exposed emulsion layer is contacted with an aquousalkaline developing composition to form a negative image in saidlight-sensitive layer and an imagewise distribution of soluble silvercomplex in terms of unexposed areas of said emulsion is transferred to astratum above said layer of said material wherein it is reduced to imagesilver to form a positive transfer image, said layer of said materialbeing present in an amount sufiicient for masking effectively saidnegative image while at the same time providing a background for saidpositive image thereover, thereby providing a composite print viewableby reflected light as apositive image; the step which comprisesincorporating a photographically innocuous humectant in said layer in anamount sufiicient to lower the processing time for forming said transferimage.

11. A process as defined in claim 10 wherein said emulsion comprises agelatino silver halide emulsion and the amount of said humectantincorporated in said emulsion layer is at least 25% by weight of thegelatin in said layer.

12. A process as defined in claim 10 wherein said humectant comprisesa-methyl-glucoside.

13. In a photographic process wherein a layer containing alight-sensitive silver halide emulsion and a light opacity-providingmaterial is exposed to form a develop able image and said exposed layeris contacted with an aqueous alkaline developing composition to form anegative image in said layer and an imagewise distribution of solublesilver complex in terms of unexposed areas of said emulsion which istransferred to a stratum above said layer where it is reduced to imagesilver to form a positive transfer image, said material being present inan amount sufficient for masking effectively said negative image whileat the same time providing a background for said positive imagethereover, thereby providing a composite print viewable by reflectedlight as a positive image; the step which comprises incorporating aphoto graphically innocuous humectant in said layer in an amountsufficient to lower the processing time for forming said transfer image.

14. A process as defined in claim 13 wherein said emulsion comprises agelatino silver halide emulsion and the amount of said humectantincorporated in said emulsion layer is at least 25% by weight of thegelatin in said layer.

References Cited UNITED STATES PATENTS 2,543,181 2/1951 Land 96292,644,756 7/1953 Land 9629 2,616,807 11/1952 Land 9629 2,662,822 12/1953Land 9629 2,966,408 3/1957 Land 9629 2,971,840 2/ 1961 Haydn et al. 96293,041,170 6/1962 Haist 9629 3,080,230 3/ 1963 Haydn et al. 96293,185,841 5/1965 Land 9629 3,248,219 4/1966 Jacobs 9629 FOREIGN PATENTS504,283 9/ 1939 Great Britain 9667 746,948 3/1956 Great Britain 9629821,507 10/1959 Great Britain 9629 878,064 9/1961 Great Britain 9629921,370 3/ 1963 Great Britain 9629 545,678 10/ 1959 Belgium 9629 GEORGEF. LESMES, Primary Examiner J. P. BRAMMER, Assistant Examiner US. Cl.X.R. 9648, 76

